ask yourself why there is a problem on just the wave solder side.....
doesn't this suggest that there is an assembly issue here ? Remember first
and foremost that ENIG takes longer to wet than HASL or tin or silver, and
wicking through holes is limited. In my experience you should look at  a)
the fluxing prior to wave solder - spray works best, b) is the wave height
correct and conveyor parallel, c) is it a double wave, d) is the soldermask
too thick - this can effectively leave the flux trapped and actually
repelling the solder before it has a time to wet e)are the soldermask
apertures too small - same effect as d)
Dougal Stewart

email:  [log in to unmask]
phone: +44 1896 822204
mob:    +44 7984 629667
----- Original Message -----
From: "Earl Moon" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Sunday, March 10, 2002 11:26 AM
Subject: [TN] ENIG AND NON WETTING


> Folks,
>
> Don't know yet for sure but I may have gotten my client and self in a bit
of
> a problem. Used this very highly qualified fab supplier for some time.
Used
> ENIG from them and other quppliers equally qualified and never had this
> issue arise and I'm not sure of the cause. I know even the best loose the
> recipe but rarely.
>
> Can't post the pictures now as I'm on a different computer without them.
The
> non wetted pads are on the wave solder side (my assembly house didn't
reflow
> the important top side using paste per my instructions. Some pads are
> partially wetted to about 50%. Many through hole pads wetted and many
didn't.
>
> The board was requested to be a solder mask over bare copper, ENIG. Type.
As
> the ENIG was the last wet chemical process, I'm trying to understand what
is
> the problem. I mean, there is no resist left as the gold looks as it
should
> and SM stripping was done over bare copper. What contamination could cause
> such problems?
>
> Thanks,
>
> Earl Moon
>
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